Jams on Columbia River bridges likely to last a lot longer

by: TRIBUNE FILE PHOTO: L.E. BASKOW - The Glenn Jackson Bridge on Interstate 205 over the Columbia River could be jammed with even more traffic as the regions population increases and the economy grows.With daily Columbia River bridge traffic climbing to pre-recession levels, Oregon transportation officials are saying that commuters could face rush-hour conditions in the Interstate 5 corridor more hours of the day.

And if population forecasts are accurate, the Portland-Vancouver area, in general, will see growing traffic congestion into 2030.

“The I-5 bridge cannot hold more vehicles at particular times of the day,” says David Thompson, public information section manager for the Oregon Department of Transportation. “If the Portland-Vancouver economy (and population) continues to expand, we’re going to see (traffic) volumes stay high for more hours.”

That’s because commuters, including an estimated 65,000 who live in Clark County but hold jobs in the Portland area, will adjust their commute times either earlier or later to avoid the worst traffic snarls.

Now, rush hours for both the I-5 and the Interstate 205 bridges begin at about 5:30 a.m. and continue to 9 a.m. every workday, with the afternoon rush starting at 2:30 p.m. and continuing until 7 p.m.

“We’re likely going to see those hours extended as (road) capacity remains full for longer periods,” Thompson says.

Bridge traffic counts

Daily traffic counts (during a 24-hour period) steadily increased every year from the early 1990s until 2005-07, when volumes peaked on the Interstate Bridge at 127,000 vehicles a day. The I-205 Glenn Jackson Bridge peaked at more than 144,000 vehicles a day.

The Great Recession then took a bite out of those totals, as people lost jobs and businesses and ports cut back on freight operations.

I-5 daily bridge traffic hit a low in 2009 with a September daily average of 122,215, down 5,285 vehicles a day from the peak. Daily averages hit a low on the I-205 bridge of 137,435 vehicles, down 6,565 a day.

In the past four years, bridge traffic has recovered to record daily levels, 128,319 and 143,161, respectively on the I-5 and I-205 bridges.

According to labor analysts in both Oregon and Washington, Portland-area employers are adding workers — more than 14,000 in the 12 months ending this year in October. Construction, manufacturing, trade and transportation and business services are among those adding the most new jobs.

Total regional employment is nearly 1.2 million, up 1.4 percent from last year, but still slightly below pre-recession levels, says Scott Bailey, labor analyst with the Washington Employment Security Department.

Meanwhile, Portland remains a net positive area for population growth, with more people moving in than moving out.

Bill Conerly, economist and business consultant in Lake Oswego, expects annual population growth in the seven-county Portland-Southwest Washington metro area of 1 percent to 1.5 percent during the next 15 to 17 years. That growth will add an estimated 600,000 to 650,000 more residents to the region’s total population of 2.29 million by 2030. That growth also will translate into more commuters.

Mitigating congestion

The Oregon Department of Transportation continues to work on ways to mitigate metro-area traffic congestion, Thompson says.

“We’re doing it by getting more information out there about traffic conditions and by more quickly removing blockages with our incidence response vehicles, especially on the I-5 bridge,” Thompson says.

The national rule of thumb, he says, is that for every minute of traffic blockage, there’s a five-minute backup behind it. A 20-minute traffic stall translates into almost two hours of backed-up traffic.

Thompson says commuters can help reduce traffic congestion by checking traffic conditions before starting their drive to work or their commute home.

If even 10 percent of drivers would delay their commute or take an alternate route because of congestion, it would make a difference in how fast tie-ups are dealt with, Thompson says. Commuters can check either Oregon’s or Washington’s Both websites offer up-to-the-minute traffic camera information on all important roads and highways. Thompson says metered ramp signals also help by more efficiently managing traffic flow.

“Ramp meters let cars fit into traffic one-by-one,” he says. “Unfortunately, drivers only feel the wait (at the ramp light) but not the gain in traffic efficiency.”

Next year, expect new electronic advisory signs on Interstate 5 that will suggest to drivers what speeds in each lane will best keep traffic moving. Seattle already has them.

“We’re trying to do things that will help with congestion, but commuters also are going to have to do stuff and make their own best judgments on what routes to take and when to take them,” Thompson says.

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